Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 220837
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
237 AM MDT THU SEP 22 2016

.SHORT TERM...(Today through Friday night)
Issued at 215 AM MDT Thu Sep 22 2016

Obs show low clouds becoming more and more widespread for areas
to the east of the Laramie Range as light northeasterly sfc winds
transport llvl moisture into the area. Expecting cigs/vis to
continue to lower through 12Z with widespread LIFR/IFR conditions.
Extended fog all the way westward to the Laramie Range through mid
morning. Temps will be about 10 degrees cooler across the plains,
especially in the Nebraska Panhandle where low clouds will likely
persist through the early aftn. Pressure falls will occur through
the day over central WY with south-to-southeasterly winds becoming
breezy by late aftn into the evening. With the best forcing
remaining over the western half of WY, kept POPs mostly in the
20-40 percent range for areas along and west of the Laramie Range
through the evening. The HRRR and NCAR ensemble is not showing much
activity over the plains and especially the Nebraska Panhandle
where the airmass will be mostly capped.

Strong closed upper low is progged to move into southwest WY by
Friday aftn with cooling aloft and upper level diffluence
increasing for areas to the east of the Laramie Range. The models
continue to be in good agreement at showing showers and isolated
tstms developing over much of the plains of southeast WY into
portions of the Nebraska Panhandle by the aftn and evening, in the
convergence along the cold front. The cold frontal passage will
occur through the evening with breezy west to southwest winds
developing by late Friday night over southeast WY as the 700 mb
CAG-CPR gradient rises to 40-50 meters.

.LONG TERM...(Saturday through Wednesday)
Issued at 215 AM MDT Thu Sep 22 2016

More Autumn like weather in store for the weekend as low pressure
slowly moves through the area. Strong cold front associated with
the low looks to move through Saturday morning. 700mb temperatures
fall below freezing, down to -2C across the mountains to our west.
Pretty good bet that the Snowy and Sierra Madre Ranges will see
snow.

Going to see an increase in winds as well Saturday as GFS 700mb
winds at 55kts. 700mb Craig to Casper height gradient in excess of
60mtrs as well. If the low continues to track the way the GFS is
forecasting, we could be looking at more winds than precip with
this low.

Cold and windy conditions continue Saturday night into Sunday with
the upper low tracking into western North Dakota. 850mb winds in
the panhandle 40-45kts, so wind headlines will probably be needed
out that way, at least Advisory level if not warning.

Freezing temperatures for lows Monday morning across much of the
CWFA as skies clear out and winds ease. Looking at 20s for lows
across southeast Wyoming and low 30s across the Panhandle.

Start warming after Monday morning as 700mb temperatures climb
back above freezing and upper ridge begins to build back into the
area.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1101 PM MDT Wed Sep 21 2016

Stratus beginning to develop over northern Nebraska Panhandle and
will move southwest into the Cheyenne area by 09Z. Could see low
ceilings lasting most of the morning for our Nebraska Panhandle
airports as well as KCYS. Generally followed latest HRRR guidance
on timing of stratus onset and duration.

&&

.FIRE WEATHER...
Issued at 215 AM MDT Thu Sep 22 2016

No fire weather concerns through the end of the week. Temperatures
will cool over the next few days, and especially after Friday
evening behind a cold front. Minimum afternoon humidity values
will mostly be above 30 percent. Along with an increase in cloud
cover, there will be a chance of showers and thunderstorms through
Friday, mostly during the afternoons and evenings.

&&

.CYS Watches/Warnings/Advisories...
WY...None.
NE...None.
&&

$$

SHORT TERM...ZF
LONG TERM...GCC
AVIATION...GCC
FIRE WEATHER...ZF



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